1.Field of the Invention
The invention relates to methods for producing fats and oils. Specifically, the invention pertains to prolonging the enzymatic activity of an enzyme used for transesterification or esterification of a substrate for the production of fats and oils by deodorization of the substrate prior to transesterification or esterification. The invention also relates to using deodorization in tandem with a purification medium.
2.Related Art
Fats and oils are composed principally of triglycerides made up of a glycerol moiety in which the hydroxyl groups are esterified with carboxylic acids. Whereas solid fats tend to be formed by triglycerides having saturated fatty acids, triglycerides with unsaturated fatty acids tend to be liquid (oils) at room temperature. Monoglycerides and diglycerides, having respectively one fatty acid ester and two alcoholic groups or two fatty acid esters and one alcoholic group, are also found in fats and oils to a lesser extent than triglycerides.
Many fats and oils are readily obtained from processing plant or animal matter. However, some fats and oils are obtained via well-known chemical or enzymatic transesterification or esterification processes. By these processes, one or more of the fatty acid groups on a glyceride is transferred, hydrolyzed or replaced with a different fatty acid group. Chemical methods require harsh alkaline conditions, high temperatures and generate wasteful by-products. The discolored fats and oils produced need to be neutralized, washed and centrifuged to remove catalysts, and ultimately bleached. In addition to these problems, chemical transesterification or chemical esterification is non-specific in the glyceride position or type of fatty acid group transferred, hydrolyzed or replaced. It is thus very difficult or impossible to produce specific fats or oils via large scale chemical catalytic processes. In contrast, enzymatic methods of transesterification or esterification are simpler, cleaner, environmentally friendly and are highly specific with respect to modifying glyceride fatty acid groups.
One family of enzymes capable of affecting this transesterification or esterification in glycerides are known as lipases. Lipases are obtained from prokaryotic or eukaryotic microorganisms and typically fall into one of three categories (Macrae, A. R., J.A.O.C.S.60:243A-246A (1983)).
The first category includes nonspecific lipases capable of releasing or binding any fatty acid group from or to any glyceride position. Such lipases have been obtained from Candida cylindracae, Corynebacterium acnes and Staphylococcus aureus (Macrae, 1983; U.S. Pat. No. 5,128,251). The second category of lipases only adds or removes specific fatty acid groups to or from specific glycerides. Thus, these lipases are useful in producing or modifying specific glycerides. Such lipases have been obtained from Geotrichum candidium and Rhizopus, Aspergillus, and Mucor genera (Macrae, 1983; U.S. Pat. No. 5,128,251). The last category of lipases catalyze the removal or addition of fatty acid groups from the glyceride carbons on the end in the 1- and 3-positions. Such lipases have been obtained from Thermomyces lanuginosa, Rhizomucor miehei, Aspergillus niger, Mucor javanicus, Rhizopus delemar, and Rhizopus arrhizus (Macrae, 1983).
The last category of enzymes have wide applicability. For example, cocoa butter consists primarily (about 70-80% by weight) of saturated-oleic-saturated (SOS) triglycerides (European published patent application no. EP 0188122 A1). It is this triglyceride composition which provides the unique characteristics by which chocolate products hold their shape at room temperature but melt slightly below human body temperature (see U.S. Pat. No. 4,276,322). These SOS triglycerides include 1,3-dipalmitoyl-2-monooleine (POP), 1(3)-palmitoyl-3(1)-stearoyl-2-monooleine (POSt) and 1,3-distearoyl-2-monooleine (StOSt). Thus, oleic acid-rich glycerides with an oleic ester group in the middle position can be incubated with palmitic and stearic acid in the presence of a 1,3-specific lipase to produce POP, POSt and StOSt, i.e., cocoa butter substitutes (U.S. Pat. No. 4,276,322). The production of cocoa butter substitutes alleviates food manufacturers from widely fluctuating cocoa butter supply and cost. 1,3-specific lipases also are useful in the manufacture of specialty 1,3-diglycerides, as described in U.S. Pat. No. 6,004,611.
Despite these benefits, enzymatic transesterification or esterification is a costly process because of the expense in providing a large amount of purified lipase. Moreover, the enzymatic activity of lipase decays with time and with exposure to large amounts of fats or oils. The present invention reduces these problems by providing an enzymatic method for producing fats or oils by which the enzymatic activity of lipase is prolonged.